Chain comprising a plurality of interconnected links

ABSTRACT

The invention relates to a chain suitable to moor or anchor boats, to lash cargo in road, rail, water and air transportation or for conveying, hoisting, suspending or lifting applications, said chain comprising a plurality of interconnected links. More in particular the invention relates to a chain suitable for the above stated uses comprising a plurality of interconnected links, at least part of the links comprising polyolefin fibers and in particular ultrahigh molecular weight polyethylene (UHMWPE) fibers. The invention also relates to a method for enhancing the strength of such a chain.

This application is a continuation of U.S. application Ser. No.12/523,920 filed on 9 Nov. 2009 (now U.S. Pat. No. 8,171,714), which isthe U.S. national phase of International Application No.PCT/EP2007/009431 filed 30 Oct. 2007, which designated the U.S. andclaims priority to European Application No. 07001305.7 filed 22 Jan.2007, the entire contents of each of which are hereby incorporated byreference.

The invention relates to a chain suitable to moor or anchor boats, tolash cargo in road, rail, water and air transportation or for conveying,hoisting, suspending or lifting applications, said chain comprising aplurality of interconnected links. More in particular the inventionrelates to a chain suitable for the above stated uses comprising aplurality of interconnected links, at least part of the links comprisingpolymeric fibres. The invention also relates to a method for enhancingthe strength of such a chain.

A chain should desirably be capable of transmitting forces under allkinds of circumstances and environmental conditions, often for aprolonged period of time, without the chain being affected in any way,such as by breaking, fraying, damaging, and so on. Other requirementsmay also be important. During use in the above-mentioned operations,chains are subjected to substantial wear and tear conditions which maylead to extensive abrasion of the chain. Chains should therefore bedurable. Chains for air transportation moreover should not only bestrong and durable, but at the same time be as lightweight as possible,in order not to unduly increase the payload of an aircraft. A chainshould also have a low risk for sudden failure. This is important insecuring air cargo, where a sudden release of heavy weight cargo may beparticularly disastrous.

A chain comprising a plurality of interconnected links, at least part ofthe links comprising polymeric multifilament yarns, is known from U.S.Pat. No. 4,779,411. The disclosed chain comprises links of aromaticpolyamide (aramid) multifilament yarns, sheathed with a woven outerfabric. Although the chain known from U.S. Pat. No. 4,779,411 performsreasonably well, its service life is limited, in particular underdynamic loading conditions.

The object of the present invention is to provide a chain according tothe preamble that is very well capable of transmitting forces andmoreover shows improved durability over the prior art.

This object is achieved according to the invention by providing a chaincomprising a plurality of interconnected links, wherein at least part ofthe links comprise polyolefin multifilament yarns.

In a chain, forces are transmitted from one link to another through theinterconnections, where links make local mutual contact. At the contactpoints the links are highly stressed (mainly compressive), which easilyleads to local damage or even fracture of the link. Surprisingly, whenusing polyolefin multifilament yarns, and ultrahigh molecular weightpolyethylene multifilament yarns in particular, in the chain links, theservice life of the chain is improved with respect to the prior art, inparticular under dynamic loading conditions.

A suture is known from US Patent Application 2006/0259076 having achain-like construction including at least two loops formed of Dyneema®(DSM) ultra high molecular weight long chain polyethylene (UHMWPE)multifilament yarns. However, the suture disclosed therein is too thinand too weak, i.e. very low static strength, to be used in heavy-dutyapplications like mooring or anchoring boats, lashing cargo in road,rail, water and air transportation or conveying, hoisting, suspending orlifting applications. Furthermore, the referred US application is silentwith regard to heavy-duty applications as the present invention relatesto. Yet furthermore, the requirements for a suture in terms of staticstrength are different than those for a chain designed for saidheavy-duty applications. No disclosure is given in the referred USapplication regarding requirements for heavy-duty applications.

A chain according to the invention shows an unexpectedly high strengthand durability and is damage tolerant. A chain according to theinvention moreover shows an improved strength retention over the priorart. When a chain is used to transmit forces under variablecircumstances, fatigue and friction induced local heat up may alsobecome important. Although polyolefin multifilament yarns in generalhave limited temperature resistance, at least compared to metals forinstance, these effects surprisingly do not occur in the chain accordingto the invention, at least not to such extent that performance ishampered.

Preferably, the static strength of the chain of the invention is atleast 1 kN, more preferably at least 5 kN, even more preferably at least10 kN, yet even more preferably at least 30 kN, yet even more preferablyat least 50 kN, yet even more preferably at least 100 kN, yet even morepreferably at least 1000 kN, yet even more preferably at least 10,000kN, yet even more preferably at least 50,000 kN, yet even morepreferably at least 100,000 kN, yet even more preferably at least150,000 kN, yet even more preferably at least 500,000 kN, mostpreferably at least 10⁶ kN.

By static chain strength is herein understood the strength of the chainwhen the chain is subjected to a static load.

Polyolefin multifilament yarns are used in the chain according to theinvention. These multifilament yarns are known per se, and have anelongated body whose length dimension exceeds the transverse dimensionsof width and thickness. The elongated bodies may have a regular orirregular cross-section. Preferably, the polyolefin multifilament yarnsused in the chain have a tensile strength of at least 1.2 GPa, morepreferably at least 2 GPa, preferably at least 3 GPa, yet even morepreferably at least 3.5 GPa, yet even more preferably at least 4 GPa,most preferably at least 5 GPa, and a tensile modulus of at least 40GPa, more preferably at least 60 GPa, most preferably at least 80 GPa.

Homopolymers and copolymers of polyethylene and polypropylene areparticularly suitable polyolefins for the production of the polyolefinmultifilament yarns. The polyolefins may contain small amounts of one ormore other polymers, in particular other alkene-1-polymers. Aparticularly preferred polyolefin comprises UHMWPE, having a weightaverage molecular weight of at least 400,000 g/mol. Preferably, theUHMWPE has less than 1 side chain per 300 C atoms, more preferably lessthan 1 side chain per 100 C atoms. The UHMWPE multifilament yarnsapplied in the chain according to the invention may further containsmall amounts, generally less than 5% by weight, preferably less than 3%by weight, of customary additives, such as anti-oxidants, thermalstabilizers, colorants, flow promoters, and so on.

Preferably UHMWPE multifilament yarns are used which comprise UHMWPEfilaments, prepared by a gel spinning process. A suitable gel spinningprocess is described in for example GB-A-2042414, GB-A-2051667, EP0205960 A and WO 01/73173 A1, and in “Advanced Fibre SpinningTechnology”, Ed. T. Nakajima, Woodhead Publ. Ltd (1994), ISBN 185573 1827. In short, the gel spinning process comprises preparing a solution ofa UHMWPE of high intrinsic viscosity in a solvent, spinning the solutioninto filaments at a temperature above the dissolving temperature,cooling down the filaments below the gelling temperature, and drawingthe filaments before, during and/or after at least partial removal ofthe solvent.

The preferred polyolefin multifilament yarn comprises a multifilamentyarn of UHMWPE with an intrinsic viscosity preferably between 5 dl/g and40 dl/g, determined in decalin at 135° C., and a yarn titre of at least50 denier, with the yarn having a tensile strength of at least 2.5N/tex, more preferably at least 3.0 N/tex, even more preferably at least3.2 N/tex, even more preferably at least 3.4 N/tex. More preferably, theyarn titer is at least 100 denier, even more preferably at least 1000denier, yet even more preferably at least 2000 denier, yet even morepreferably at least 3000 denier, yet even more preferably at least 5000denier, yet even more preferably at least 7000 denier, most preferablyat least 10000 denier. Preferably, the polyolefin and more in particularthe UHMWPE multifilament yarns forming a chain link have a total titreof at least 1×10^(n) dtex, wherein n is an integer of preferably atleast 3, more preferably at least 4, even more preferably at least 5,yet even more preferably at least 6, yet even more preferably at least7, yet even more preferably at least 8, most preferably at least 9. Ifdesired, the UHMWPE multifilament yarns may comprise a mixture of two ormore polyethylenes, differing for instance in intrinsic viscosity,molecular weight distribution, and/or type and number of comonomers orside chains. The intrinsic viscosity is determined according to PTC-179(Hercules Inc. Rev. Apr. 29, 1982), adopting a dissolution time of 16hours, using an amount of 2 g/l solution of DBPC as anti-oxidant,measuring the viscosity at different concentrations, and extrapolatingto zero concentration. Tensile strength (or tenacity) of the UHMWPEmultifilament yarns is determined according to ASTM D885M.

A further advantage of the use of polyolefin multifilament yarns, andparticularly UHMPWE multifilament yarns, in the links of a chain is thatan unexpectedly high static chain strength is obtained. The durabilityunder fatigue loading, and/or the strength in humid conditions are alsoimproved over the prior art. Humid conditions refer to environmentswherein the degree of humidity is on average higher than 50%, morepreferably higher than 80% and most preferably higher than 99%. Byfatigue loading is herein understood dynamic loading conditions.

The chain is further advantageously used in marine applications forinstance, where the chain comes in direct contact with water.

The chain according to the invention has a low specific gravity, whichmakes it particularly suitable in applications where low weight isimportant. Further, its environmental resistance is good, particularlyagainst acids. Other advantages include its softness, low noise andnon-corrosive characteristics, ease of handling, and ease of deployment.The chain moreover does not substantially conduct electrical currentand/or heat, is relatively non-magnetic, and has a relatively lowdielectric constant. It also exhibits low radar and infrared signature,which may be advantageous for military applications for instance.

Another preferred embodiment of the chain according to the invention ischaracterised in that at least part of the links comprise glass fibers,carbon fibers, metal fibers, aromatic polyamide fibers,poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers, M5 fibers, and/orpoly(tetrafluoroethylene) (PTFE) fibers. The term fibers includes but isnot limited to a filament, a multifilament yarn, a tape, a strip, athread, a staple fibre yarn, and other elongated bodies may have havinga regular or irregular cross-section. According to another preferredembodiment, at least part of the links of the chain consists of saidfibres. Such a chain may have different properties along the length ofthe chain. For instance, some parts of the chain may have mechanicalproperties favourable to withstanding dynamic loading conditions, whileother parts may have mechanical properties favourable to withstandingstatic loading conditions. Another possibility is that parts of thechain may be made lighter than water (these parts will generallycomprise polyolefin multifilament yarns) while other parts may be madeheavier than water. It is also possible that some links comprise saidfibers in combination with polyolefin multifilament yarns, for examplein the form of hybrid yarns. More preferred, at least part of the linkscomprise at least 51 vol. % of UHMWPE multifilament yarns, even morepreferred at least 75 vol. %, even more preferred at least 90 vol. %,and most preferred at least 95 vol. %. A particularly preferred chain ischaracterised in that all links consist of UHMWPE multifilament yarns.

A further advantage of the use of polyolefin multifilament yarns, andmore in particular UHMWPE multifilament yarns, is that a more reliablechain is obtained than the known chains, based on metal or on otherpolymeric fibres, such as aromatic polyamide fibers, for instance.

The multifilament yarns or fibers may have any construction known in theart, and/or may be combined in any textile construction known in theart. It is possible for instance to make the links of the chain in theform of endless loops of fibre bundles or yarns, extending more or lessparallel to each other. A particularly preferred chain has links thatcomprise at least partly fused polyolefin multifilament yarns. Linksthat comprise at least partly fused polyolefin multifilament yarns maybe present in the chain in the form of rings, loops, roundslings, and soon, and preferably also comprise a cover for protection and/or loaddistribution. Links that comprise at least partly fused polyolefinmultifilament yarns may be manufactured by winding a multifilament yarnof the polyolefin around a pair of wheels to form a loop, heating themultifilament yarn to a temperature below the melting point of themultifilament yarn at which temperature the filaments at least partlyfuse, and stretching the loop by increasing the distance between thewheels, while simultaneously rotating the wheels. By increasing theinter-wheel distance, the filaments are drawn. Chains comprising suchlinks are strong and moreover distribute the loads between linksparticularly well.

Particularly preferred chains are characterised in that the linkscomprise straps of polyolefin multifilament yarns. By strap is meantherein a flexible, elongated body having a thickness that is muchsmaller than its width. Such straps are readily made by weaving orknitting the multifilament yarns into any construction, known in theart, such as a plain and/or twill weave construction for instance. Thestraps preferably have an n-ply webbing construction, where n ispreferably at least 4, more preferably 3 and most preferably 2. Thestraps can be constructed with different tightness factors to adjusttheir mechanical properties, and more in particular their elongation tobreak. Preferred tightness factors are such that the straps have anelongation at break of at most 6%, and more preferred at most 4%. Thetightness factor is herein defined as the number of yarns extendingparallel to the longitudinal direction of the strap multiplied by thetitre of the yarn per unit length. The width of the straps may be variedover a large range, with preferred widths at least 1.0 cm, morepreferred at least 2.0 cm, even more preferred at most 30 cm, and mostpreferred at most 25 cm. The thickness of the straps is preferablychosen such that their ratio of width to thickness is at least 5:1, morepreferably at least 10:1, the ratio of width to thickness moreoverpreferably being at most 40:1, and even more preferably at most 20:1. Bylimiting the width to thickness ratio of the straps, the links of thechain are more easily accessible for attachment means, such as hooks forinstance.

In another preferred embodiment of the invention the chain linkscomprise an endless rope or tape, generally called a rope or tape sling.The advantage of a roundsling is that connections to each other or to afitting having an eye for instance can be made with simple known knots,hitches or bends, which also show relatively high knot strengthretention. Such a knot is for example the cow hitch, also called balesling hitch, ring hitch, or tag knot. Such a knot can be made by passingone loop end of the sling through an eye, or a mesh, and then passingthis loop through the opening formed by the other end of the sling (alsocalled tail), and subsequently pulling the first end to tighten theknot. The person skilled in the art may easily select other suitableknots, for example the so-called double ring hitch, the Kellig hitch, orPrusik and Klemheist knots. These and other knots, and methods to makethem can be found in the ‘Handbook of knots’, (Dorling Kindersley Book,London 1998; ISBN 0751305367), and in “The Ashley book of knots’ (Faberand Faber Ltd, London 1990; ISBN 057109659x).

A rope or tape sling can be made by known methods, for example byconnecting a certain length of rope or webbing end-to-end by sewing,knotting, splicing or welding. For ropes, preferably, the thickness ofthe end-to-end connection is less than twice the thickness of the rope,because this improves the flexibility and ease of connecting to afitting. In one embodiment, the sling is made by sewing both ends of awoven strap together. In another embodiment the ends of a braided orlaid rope are connected with a splice. A sling is within the presentapplication understood to include a double loop, or double eye, or atriple eye. Such constructions are known to the skilled person, and canfor example be made by splicing a loop on each end of a rope, or bymaking one or more connections, e.g. by sewing, preferably in the middlepart of a sling. Preferably, the sling is coated and/or covered withtape or with a fabric to protect the fibres and/or to increase furtherits abrasion resistance. The sling may also comprise a core formed by aplurality of windings of multifilament yarns, preferably essentiallyparallel multifilament yarns, and a covering sheath, e.g. a woven orbraided tubular fabric, and/or a sheath made from polyester, (aromatic)polyamide, or polyolefin multifilament yarns, or from a mixture thereof.Another advantage of the chain according to the invention is that acovering sheath is not necessary to obtain the desired performance.

Preferably, at least part of the links of the chain comprisesmultifilament yarns that have been combined with a suitable resin. Anyresin able to form a suitable composite with the multifilament yarns maybe used, although silicone resins and bitumen are the preferred resins.A chain according to this embodiment has links which deform to a lesserextent when the chain is stretched. This is advantageous when objects,such as hooks for instance, have to be attached to the chain especiallywhen the chain is under load. The resin also offers further protectionagainst damage development during dynamic loading conditions forinstance.

The chain structure may be any structure known in the art. A preferredembodiment of the chain according to the invention is characterised inthat the links of the chain comprise interconnected endless loops. Suchchains are easily tailored according to their needs. For instance, theirlength is easily adjusted by adding or removing loops. Adding loops isfor instance carried out by running several windings of the fiberthrough an existing loop, and subsequently securing the newly made looppreferably by stitching. Also side chains may easily be added to the(main) chain in a similar manner. This embodiment of the chain accordingto the invention also has an improved strength, since the loops areendless, and therefore do not have many cut ends.

The endless loops may also be interconnected by all means known in theart. The many options available to interconnect the loops is at leastpartly due to the use of UHMWPE multifilament yarns in the chain,particularly since these multifilament yarns show an improved loaddistribution capability over other polymeric multifilament yarns.Preferably the interconnected endless loops are interconnected by knots.This does not substantially affect chain performance, and is a veryexpedient way of interconnecting the loops. Another preferred embodimentis characterised in that the interconnected endless loops areinterconnected by tubular connecting means. Such means offer improvedload distribution, and are preferably filled with another material, suchas a resin.

Another preferred chain structure according to the invention comprises aladder. Such a ladder structure is easily made, out of rope forinstance, and provides improved strength. Moreover, the links in such aladder structure are deformable, yet provide easy access for other partssuch as fixation means in the form of hooks for instance.

In still another embodiment the chain according to the invention ischaracterised in that the links are interconnected by connecting meanswhich are preferably ring shaped. In such an embodiment the linkspreferably comprise straps of UHMWPE multifilament yarns. They may beattached to the connecting means by any suitable means, but preferablyby stitching. In a preferred embodiment, the ring shaped connectingmeans may have different shapes as for example a circle, an oval, atriangular or a rectangular shape and may be made of any suitablematerial, including metal.

The components of the chain, such as the links and the connecting means,may be fixed to each other and/or to another structure by applying anysuitable fixation means. Suitable fixation means include stitches,splicing and adhesives for instance. Preferably, the fixation means arestitches, because they can be easily applied in a well-controlledmanner, at the desired location. Preferably, stitching is done with ayarn containing high-strength fibers.

In a further embodiment the fixation means are adhesives, preferablyliquid adhesives that can be cured after application. The liquidadhesive is preferably injected into the connection means, such as anapplied knot, and then cured to fixate the connection means. Connectionscan also be made by locally applying heat whereby the multifilamentyarns at least partly melt and fuse together.

The chain according to the invention may also comprise means to attachit to another structure such as a pallet for instance. In this case,pallet attachment fittings, such as double studs, may be connected tothe chain. Fittings, and hooks, are generally made from metal, althoughengineering plastics could alternatively be used. In a preferredembodiment, fittings and hooks are made of light weight metal,preferably magnesium. Such light-weight yet strong fittings furthercontribute to weight reduction of the chain.

The invention also relates to a method to enhance the mechanicalproperties, in particular the strength of a chain according to theinvention.

It was found that the mechanical properties of the chain according tothe invention, in particular its strength can be improved bypre-stretching the chain prior to its use below the melting point of thepolyolefin, more preferably between 80-120° C., and most preferablybetween 90-110° C.

In a preferred embodiment of the method, the chain according to theinvention is pre-stretched at a temperature below the meltingtemperature T_(m) of the polyolefin, by applying a static load of atleast 20%, more preferably at least 40%, and most preferably at least60% of the breaking load of the chain for a period of time long enoughto achieve a permanent deformation of the chain of between 2 and 20%,and more preferably between 5 en 10%. By permanent deformation is hereinunderstood the extent of the deformation from which the chain cannotanymore recover.

In a second preferred embodiment of the method, the chain according tothe invention is subjected to a number of load cycles. Preferably, thenumber of cycles ranges from 2-25, more preferably from 5-15, and mostpreferably from 8-12, whereby the maximum load applied is lower than 45%of the breaking load of the chain, more preferably lower than 35% of thebreaking load of the chain, and most preferably lower than 25% of thebreaking load of the chain. It is possible according to the invention tounload the chain during load cycling. In a preferred method however, theminimum load applied is at least 1%.

In a fourth preferred embodiment, the chain is pre-stretched asexplained hereinabove at room temperature.

The invention will now be further explained by the following figures,without however being limited thereto. Herein:

FIG. 1 schematically represents a first embodiment of a chain accordingto the invention;

FIG. 2 schematically represents an improvement of the embodiment shownin FIG. 1;

FIG. 3 schematically represents two loops of another improvement of theembodiment of FIG. 1;

FIG. 4 schematically represents another embodiment of a chain accordingto the invention;

FIG. 5 schematically represents a detail of the embodiment shown in FIG.4; and

FIGS. 6, 7 and 8 schematically represent three other embodiments of achain according to the invention.

Referring to FIG. 1 a chain 1 is shown comprising a plurality ofinterconnected links 10. The links 10 comprise interconnected endlessloops, made by successively inserting a second open loop into a firstalready closed loop, and closing the second loop, for instance by usingknown techniques utilized in the textile industry, such as stitching,and/or by adhesive bonding. The loops 10 are roundslings, but anyfibrous structure may be used. The connections 20 between the links 10are formed by parts of the loop surfaces, which upon stretching of chain1 impinge upon each other. This way of load transfers between links 10results in locally high (compressive) stresses. The use of ultrahighmolecular weight polyethylene multifilament yarns in the links providesimproved resistance against these stresses. Another advantage is thatchain 1 can be easily adjusted in length by attaching more links to analready existing part, or by removing links. It is also very easy to addside-links to the chain. Links 10 may have any form, may differ fromeach other, and may extend in different planes, as shown in FIG. 1 wherelinks 10 a are in the plane of the figure, and links 10 b perpendicularthereto.

FIG. 2 shows an improvement over the chain of FIG. 1. This embodimenthas interconnected endless loops 10 that are interconnected by tubularconnecting means 21. Connecting means 21 preferably have an innersurface shaped such that load transfer between loops 10 is welldistributed. Connecting means 21 may be filled with resin to obtain amore rigid connection between the loops 10. A further advantage of thisembodiment is that the loops 10 are more easily accessible for hooksand/or other loops and the like, since the connecting means 21 act tokeep the loops 10 open, at least in their vicinity.

Another preferred variant of the chain is shown in FIG. 3. Here, theinterconnected endless loops 10 are interconnected by knots 22, inparticular a cow-hitch knot. Although only two loops 10 are shown inFIG. 3, a chain obviously will have many more loops 10 in general.

Still another preferred embodiment of the chain according to theinvention is shown in FIGS. 4 and 5. Referring to FIG. 4, the chain 1comprises a ladder structure, consisting of stiles 22 and steps 23.Stiles 22 and steps 23 together define a plurality of loops 10. Steps 23form the connection between the loops 10. The ladder 1 may be made ofany suitable fibrous structure, such as a rope, a webbing, a sling, ayarn, and so on. FIG. 5 shows a detail of how stiles 22 and steps 23 canbe continuously formed of ultrahigh molecular weight polyethylene rope.The left figure shows an expanded view of the structure in thisparticular embodiment. Not only can a ladder chain 1 be made out ofessentially one rope, which offers improved load transfer at theconnections, but this particular embodiment also allows to readilyincorporate additional attachment structures, such as eyes 25 for hooksor other attachment means 26.

Referring to FIG. 6, still another embodiment of the chain 1 accordingto the invention is shown. The chain 1 has a plurality of loops 10 inthe form of ultrahigh molecular weight polyethylene fibrous structures,such as yarns and/or slings, interconnected by wraps 27 of anotherfibrous structure, preferably also out of ultrahigh molecular weightpolyethylene. The chain further has a hook 28 attached to it, and a ring29. The connection of ring 29 to the rest of the chain is formed by astrap 30, preferably also out of ultrahigh molecular weightpolyethylene. This embodiment shows that a chain can easily be build upfrom several components, thereby providing great flexibility in use.Several components, such as hook 28, and ring 29 may be made fromanother material, such as metal, if desired.

In FIGS. 7A and 7B another preferred embodiment of the chain 1 is shown.FIG. 7A is a side view, while FIG. 7B represents a top view. Chain 1 isbuild up of loops 10 in the form of rings. Rings 10 are formed bywinding several layers of a fibrous structure of ultrahigh molecularweight polyethylene. Three layers (a to c) are shown, but there may bemore or less, depending on the desired loads bearing capacity. Thelayers of rings 10 are held together by bonding them, for instance bystitchings 11. Rings 10 are interconnected by looped straps 31, oppositesides of which are bonded over at least a central portion 32. Bindingcan be done by stitches 33, but other means of bonding may also be used.If desired, stitches 33 may be omitted, for instance when a moreflexible chain is needed.

Finally FIG. 8 shows still another embodiment of the chain 1 accordingto the invention. This chain 1 is build up of U-shaped fibrousstructures 10, which form the links of the chain. Each structureconsists of several layers of a fibrous structure of ultrahigh molecularweight polyethylene. Three layers (a to c) are shown, but there may bemore or less, depending on the desired loads bearing capacity. TheU-shaped links 10 are assembled and attached to two stiles 34, alsobuild of several layers of a fibrous structure of ultrahigh molecularweight polyethylene, in the variant shown two layers (d, e). Links 10and stiles 34 are bonded to each other, for instance by stitching. InFIG. 8 stitches 35 are shown for one link only.

The present invention will now be further elucidated by the followingexamples and comparative experiments. Tests comparing the invention withthe prior art, according to U.S. Pat. No. 4,779,411 (chain based onaramid) were conducted. A first series of tests included tensile testingof yarns and tensile testing of chains, made of these yarns. A secondseries of tests included abrasion tests, carried out on chains under dryand wet conditions.

Tensile testing was performed on dry samples using a Zwick 1484Universal test machine at a temperature of approximately 21° C., and ata speed of 100 mm/min. Yarn samples were tested using standard fibergrips; chain samples were tested using D-shackles.

Abrasion testing was performed on a spoke wheel abrasion tester StaticAbrasion Test, used in the rope and cable industry. The sample is incontact with a rotating body (spoke wheel, diameter 0.15 m) thatcontains 20 rods of 15 mm diameter parallel to the rotation axis of thebody. The sample is loaded, usually with a certain fraction of thebreaking load. The test can be done dry or wet, in the latter situationthere is a continuous feed of water to the part of the sample in contactwith the spoke wheel. The speed of the wheel was 2 rotations/sec, theload on the chain sample was 6% of the breaking strength. The number ofcycles until failure was recorded.

EXAMPLE I

The breaking load and tenacity of Dyneema® SK75 yarn of 1760 dtex (=1760g for 10000 m), obtained from DSM Dyneema B.V., the Netherlands, weredetermined. Tensile testing was performed as mentioned above. Resultsare summarized in Table 1.

EXAMPLE II

The breaking load and tenacity of a chain, made of Dyneema® SK75 yarn ofDSM Dyneema B.V., the Netherlands, were determined. The chain had 4engaging loops of 16 Dyneema® SK75 yarns of 1760 dtex. The sample chainswere fixed by air-splicing. Tensile testing was performed as mentionedabove. Results are summarized in Table 1.

Comparative Experiment A

The breaking load and tenacity of Twaron® 2000 yarn of 1580 dtex (=1580g for 10000 m), obtained from Tejin Twaron, B.V., the Netherlands, weredetermined. Tensile testing was performed as mentioned above. Resultsare summarized in Table 1.

Comparative Experiment B

The breaking load and tenacity of a chain, made of Twaron® 2000 yarn ofTejin Twaron, B.V., the Netherlands, were determined. The chain had 4engaging loops of 20 Twaron® 2000 yarns of 1580 dtex. The sample chainswere fixed by air-splicing. Tensile testing was performed as mentionedabove. Results are summarized in Table 1.

TABLE 1 Results of tensile tests on yarns and chains Weight BreakingTenacity Strain Sample (dtex) load (N) (cN/dtex) (%) Example I 1760 60634.3 3.6 Comparative Exp. A 1580 309 19.6 2.7 Example II 56400 2835 5.033.2 Comparative Exp. B 63200 2364 3.8 2.6

EXAMPLE III

The number of cycles until failure was determined of a dry chain, madeof Dyneema® SK75 yarn of DSM Dyneema B.V., the Netherlands. Three chainswere tested. The chain had 4 engaging loops of 16 Dyneema® SK75 yarns of1760 dtex. The sample chains were fixed by air-splicing. Abrasiontesting was performed as mentioned above. Results are summarized inTable 2.

EXAMPLE IV

The number of cycles until failure was determined of a wet chain, madeof Dyneema® SK75 yarn of DSM Dyneema B.V., the Netherlands. Three chainswere tested. The chain had 4 engaging loops of 16 Dyneema® SK75 yarns of1760 dtex. The sample chains were fixed by air-splicing. Abrasiontesting was performed as mentioned above. Results are summarized inTable 2.

Comparative Experiment C

The number of cycles until failure was determined of a dry chain, madeof Twaron® 2000 yarn of 1580 dtex (=1580 g for 10000 m), obtained fromTejin Twaron, B.V., the Netherlands. Three chains were tested. The chainhad 4 engaging loops of 20 Twaron® 2000 yarns of 1580 dtex. The samplechains were fixed by air-splicing. Abrasion testing was performed asmentioned above. Results are summarized in Table 2.

Comparative Experiment D

The number of cycles until failure was determined of a wet chain, madeof Twaron® 2000 yarn of 1580 dtex (=1580 g for 10000 m), obtained fromTejin Twaron, B.V., the Netherlands. Three chains were tested. The chainhad 4 engaging loops of 20 Twaron® 2000 yarns of 1580 dtex. The samplechains were fixed by air-splicing. Abrasion testing was performed asmentioned above. Results are summarized in Table 2.

TABLE 2 Results of abrasion tests on chains Sample #1 #2 #3 AverageExample III 642 631 651 641 Comparative Exp. C 70 74 91 78 Example IV2228 2091 2726 2348 Comparative Exp. D 105 127 104 112

EXAMPLES V TO VIII

Finally, a chain was made using a strap, made of Dyneema® SK75 1760 dtexyarn of DSM High Performance Fibers B.V. The strap had a linear weightof 238000 dtex (Example V). From the straps several chains were producedhaving the structure of FIG. 7. The chains are composed of rings, therings being formed of 4 wraps of the above mentioned strap and stitchedtogether. In the chain of Example VI, the rings as produced had acircular shape. The chain of Example VII had rings as produced with arectangular shape. Also a pretension was applied to the rings beforethey were stitched together. Finally, the chain of Example VIII wasequal to that of example VII, but the chain was heat set at atemperature of 100° C. applying a permanent strain of 5%. Tensiletesting was performed as mentioned above. Results are summarized inTable 3.

TABLE 3 Results of tensile tests on chains Weight Breaking load TenacitySample (dtex * 1000) (N * 1000) (cN/dtex) Example V 238 42 17.6 ExampleVI 1900 105 5.5 Example VII 1900 115 6.1 Example VIII 1800 130 7.2

From the tensile test results mentioned above it can be concluded thaton the basis of equal weight, a chain based on ultrahigh molecularweight polyethylene fiber is at least about 33% stronger than a chainbased on aromatic polyamide fibers, according to U.S. Pat. No.4,779,411. Indeed from Table 1 one learns that the tenacity of a chainbased on ultrahigh molecular weight polyethylene fiber (Example II) is5.0 cN/dtex, while the tenacity of a chain based on aromatic polyamidefibers (Comp. Exp. B) is only 3.8 cN/dtex.

From the abrasion test results mentioned above it can be concluded thata chain based on ultrahigh molecular weight polyethylene fiber shows amuch improved service life during dynamic loading conditions than achain based on aromatic polyamide fibers, according to U.S. Pat. No.4,779,411. Indeed from Table 2 one learns that the number of cyclesuntil failure of a chain based on ultrahigh molecular weightpolyethylene fiber (Example III) is 641, while the number of cyclesuntil failure of a chain based on aromatic polyamide fibers (Comp. Exp.C) is only 78 (about a factor of 8 shorter). For a wet condition thenumber of cycles until failure of a chain based on ultrahigh molecularweight polyethylene fiber (Example IV) is 2348, while the number ofcycles until failure of a chain based on aromatic polyamide fibers(Comp. Exp. D) is only 112 (about a factor of 20 shorter).

1. A chain suitable to moor or anchor boats, to lash cargo in road,rail, water and air transportation and for conveying, hoisting,suspending and lifting applications, said chain comprising a pluralityof interconnected links, wherein at least part of the links comprisepolyolefin fibers having a tenacity of at least 1.9 N/tex.
 2. The chainaccording to claim 1, wherein it has a static strength of at least 1 kN.3. The chain according to claim 1, wherein the polyolefin is ultrahighmolecular weight polyethylene.
 4. The chain according to claim 1,wherein at least part of the chain links comprise a cover.
 5. The chainaccording to claim 1, wherein at least part of the links comprise glassfibers, carbon fibers, metal fibers, aromatic polyamide fibers,poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers, M5 fibers, and/orpoly(tetrafluoroethylene) (PTFE) fibers.
 6. The chain according to claim1, wherein the links comprise at least partly fused polyolefin filamentsand/or staple fibers.
 7. The chain according to claim 1, wherein thelinks comprise straps of polyolefin fibers.
 8. The chain according toclaim 1, wherein the interconnected links of the chain compriseinterconnected endless loops.
 9. The chain according to claim 1, whereinthe interconnected endless loops are interconnected by knots.
 10. Thechain according to claim 1, wherein the interconnected endless loops areinterconnected by tubular connecting means.
 11. The chain according toclaim 1, wherein the chain comprises a ladder structure.
 12. The chainaccording to claim 1, wherein the links are interconnected by ringshaped connecting means.